This is situated at Fort just under Ceylinco tower, This is right in front of Bank of Ceylon and Twin towers. If you at Galle face you can walk across to this place and Dutch hospital. Unless you go and search of this place you will miss it.
The last king of Ceylon King Wickramarajasinghe (Arrested at Kandy in 1815) before he is deported to India for his execution he was kept at this place (cell) you can see the actual last things there, worth a visit
There is no entry fee.